Where should I put my application logic code?

[Wei Li]

Hi,

This could be a silly question:) . I am going to build up some application logic. So I will create a few class and functions. Looks like it's not very good to put these code under controllers. Although from the manual, it says controller folder is for application logic and workflow. See if I have a function

def foo():
     return <SOME_SENSITIVE_INFORMATION>

I don't want to put this function in controllers/default.py because people can see the return value of foo() through http://myapp/default/foo which is not expected. I just want foo() to be a normal function instead of a controller function.

So my question is where is the best place to put my own application logical codes indeed? There are three places that I can put python codes into:

• models describe a representation of the data as database tables and relations between tables.
• controllers describe the application logic and workflow.
• modules are other optional Python modules.
  

Looks like to me modules is the best place. But the new problem is the global objects and classes are not visible to files in modules unlike files in models/controllers. I am not sure which packages need to be imported. It will be convenient if modules folder can be treated same as models/controllers?

Any suggestion is appreciated.

Thanks,

Wei

[黄祥]

granma said : 'everything is wonderful if you know how to appreciate it'

imho 

models :

yet in the books said that is better to not put the logic function in models

• Minimize the code in models: do not define functions there, define functions in the controllers that need them or - even better - define functions in modules, import them and use those functions as needed.

i think it because the models is execute everytime the apps running, but if you define response.models_to_run you can minimalize the unnecessary function to load or execute that you define in models everytime the apps is running.

controllers :

this is the place where programmers usually put the logic function.

modules :

i think this is same like controllers with some of benefits.

1. you can call it the logic function define in modules in other application.

2. the web2py modules is like python modules, it automatically compile it, so you will got *pyc for every module you create in here, and i think it will increaase the performance in byte compile rather in script.

just a suggestion if you want to create function that can't be execute or retrieve via browser (people can't see the return value) i think, it's better to put the __ in the function name.

e.g.

def __check_purchase_status():

please correct and forgive me if i'm wrong.

best regards,

stifan

[Anthony]

2. the web2py modules is like python modules, it automatically compile it, so you will got *pyc for every module you create in here, and i think it will increaase the performance in byte compile rather in script.

Note, if you use admin to compile the application, you get the same benefit for models, controllers, and views as you do for bytecode compiled modules.

 

just a suggestion if you want to create function that can't be execute or retrieve via browser (people can't see the return value) i think, it's better to put the __ in the function name.

e.g.

def __check_purchase_status():

Yes, this is true. Also, any function in a controller that takes arguments will not be accessible via URL, for example:

def foo(bar):
    ...

 Anthony

[Anthony]

Looks like to me modules is the best place. But the new problem is the global objects and classes are not visible to files in modules unlike files in models/controllers. I am not sure which packages need to be imported. It will be convenient if modules folder can be treated same as models/controllers?

See http://web2py.com/books/default/chapter/29/04/the-core#Accessing-the-API-from-Python-modules.

Anthony

[Phil Hughes]

Add an argument to the function: foo(bar):  Only functions with no arguments can be called from the outside world.

[Wei Li]

Thank you all for the replies! 

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[Alex]

I've quite a lot model files (~40), so far the performance is still very good. Since it is not very optimal and also not good in the long run I'm now thinking of rewriting the code into modules.

I'm struggling a little bit to rewrite the functions. E.g. consider following function in a model:

@cache('room.count', 3600, cache.ram)
def getRoomCount():
  return db(db.room.id > 0).count()

how do I write this in a module so I can access cache?

thanks,

Alex

[Anthony]

If you want to do it with a decorator, you can use @lazy_cache (see http://web2py.com/books/default/chapter/29/04/the-core#Accessing-the-API-from-Python-modules). Otherwise, you can just use current.cache to store the return value of the function.

Anthony

[Alex]

thanks Anthony!

it's working with lazy_cache decorator. I guess the @ is missing in the documentation example:

lazy_cache('key', time_expire=60, cache_model='ram')
def f(a,b,c,): ....

Alex

[Alex]

It's working fine locally but when I try to run it on the server (compiled application) I get the following error:

ImportError: No module named myapp.modules.room

any idea what I could be missing?

on the server the module .py files are under myapp/modules 

Alex

[黄祥]

i think it related with module name, try to change your module file name into unique name. i usually use the app name with the controller file name. e.g.

modules/myapp_mycontroller.py

of course you can use whatever module file name as you want, but please make it unique.

best regards,

stifan

[Alex]

thanks! that's a good tip. Unfortunately the error still exists:

ImportError: No module named myapp.modules.myapp_room

the file modules/myapp_room.py exists on the server. what else could be missing?

Alex

[黄祥]

it's hard to help you track the error. please try to create the module from simple like in the book. e.g.

/test/modules/justforlearn.py

from gluon import *

def ip(): return current.request.client

/test/controllers/default.py

from gluon.custom_import import track_changes; track_changes(True)

import justforlearn

def index():

    return "Your ip is " + justforlearn.ip()

what did you get?

if not please show your code.

p.s.

from gluon.custom_import import track_changes; track_changes(True) is not recommended on production because of overhead, 

if you not use from gluon.custom_import import track_changes; track_changes(True), please try to restart the web2py to take effect the change you made.

ref:

https://groups.google.com/forum/#!topic/web2py/tdyEQ7CJhmE

best regards,

stifan